Liquid crystal display

ABSTRACT

Disclosed is a liquid crystal display comprising: a pair of opposed substrates; a liquid crystal layer disposed between the pair of substrates, the liquid crystal layer having a display alignment state and a non-display alignment state which differ from each other and being subjected to an initialization process so as to be changed from the non-display alignment state to the display alignment state before an image is displayed; storage capacitor electrodes provided on one of the pair of substrates; pixel electrodes provided so as to overlap with the storage capacitor electrodes with an insulator interposed therebetween and disposed between the storage capacitor electrode and the liquid crystal layer, the pixel electrode having a lack portion in a region overlapping with the storage capacitor electrode; and drive means for generating potential difference between the storage capacitor electrode and the pixel electrode to thereby perform the initialization process.

FIELD OF THE INVENTION

[0001] The present invention relates to a liquid crystal display, andmore particularly to a liquid crystal display comprising an OCB-mode(Optically Self-Compensated Birefringence mode) liquid crystal displaypanel.

BACKGROUND OF THE INVENTION

[0002] In recent years, with advance in multimedia technologies, a greatdeal of image information has been distributed. As a means fordisplaying such image information, liquid crystal displays have rapidlyspread. This is because liquid crystal displays with high contrast andwide viewing angle have been developed and put to practical use withdevelopment of liquid crystal technologies. At present, the liquidcrystal displays are equal to CRT (Cathode Ray Tube) displays in displayperformance.

[0003] However, current liquid crystal displays are not suitable for usein display of moving images because of a low response speed of liquidcrystal. While it is required that the liquid crystal respond within oneframe period (16.7 msec) in a current NTSC (National Television StandardCommittee) system, the current liquid crystal displays require more than100 msec to respond between gray scales in multiple gray scale display,thereby causing a displayed moving image to be blurred. In particular,since the response between gray scales in a region where a drive voltageis low is extremely slow, a satisfactory moving image display is notattained.

[0004] Accordingly, many attempts have been conventionally made toprovide high-speed responsive liquid crystal displays. While variousliquid crystal display methods of high-speed response have beensummarized by Wu et al. (C. S. Wu and S. T. Wu, SPIE, 1665, 250 (1992)), methods capable of achieving a response characteristic necessary fordisplaying the moving image are limited.

[0005] Currently, liquid crystal displays comprising an OCB-mode liquidcrystal display panel, a ferroelectric liquid crystal display panel, oran anti-ferroelectric liquid crystal display panel are believed to bepromising as liquid crystal displays having high-speed responsivenesssuitable for display of the moving image.

[0006] Among these liquid crystal display panels, the ferroelectricliquid crystal display panel and the anti-ferroelectric liquid crystaldisplay panel having a layered structure suffer from many problemsassociated with their practical uses such as: low shock resistance,limited range of available temperatures, and high temperature dependencyof property. In view of these, attention has been focused on theOCB-mode liquid crystal display panels using nematic liquid crystal asliquid crystal displays suitable for display of the moving image.

[0007] The high-speed responsiveness of the OCB-mode liquid crystaldisplays was demonstrated by J. P. Bos in 1983. Since it was thereafterdemonstrated that the provision of retardation films brought aboutdisplays with wide viewing angle and high-speed responsiveness, theOCB-mode liquid crystal display panels have been studied and developed.

[0008]FIG. 36 is a cross-sectional view schematically showing aconstitution of the conventional OCB-mode liquid crystal display panel.Referring to FIG. 36, the OCB-mode liquid crystal display panelcomprises a first glass substrate 81 provided with a transparent counterelectrode 82 on a lower surface thereof and a second glass substrate 88provided with a transparent pixel electrode 87 on an upper surfacethereof. A first alignment layer 83 is formed on a lower surface of acounter electrode 82 and a second alignment layer 86 is formed on anupper surface of the pixel electrode 87. Liquid crystal molecules havebeen filled into a gap between these alignment layers 83, 86 to beformed into a liquid crystal layer 84. The alignment layers 83, 86 havebeen subjected to alignment treatment to align the liquid crystalmolecules in parallel with one another and in the same direction. Thethickness of the liquid crystal layer 84 is defined by a spacer 85.

[0009] A first polarizer 91 is provided on an upper surface of the firstglass substrate 81 and a second polarizer 92 is provided on a lowersurface of the second glass substrate 88. These polarizers 91, 92 areprovided in cross nicole, that is, such that their optical axes areorthogonal to each other. A first retardation film 89 is providedbetween the first polarizer 91 and the first glass substrate 81 and asecond retardation film 90 is provided between the second polarizer 92and the second glass substrate 88. As the retardation films 89, 90,negative retardation films whose main axes are hybrid-arranged are used.

[0010] In the OCB-mode liquid crystal display panel so constituted, byapplication of a voltage, the liquid crystal is caused to transitionfrom spray alignment 84 a to bend alignment 84 b, in which state, animage is displayed. Since the response speed of the liquid crystal ofthe OCB-mode liquid crystal display panel is significantly improved ascompared to a TN-mode (Twisted nematic mode) liquid crystal displaypanel, the liquid crystal display panel suitable for moving imagedisplay is realized. In addition, the provision of the retardation films89, 90 can achieve wide viewing angle.

[0011] As described above, the OCB-mode liquid crystal display paneldisplays an image when the liquid crystal is in the bend alignmentstate. Therefore, an initialization process for transitioning frominitial spray alignment to bend alignment (herein after simply referredto as spray-bend alignment transition) is essential.

[0012] FIGS. 37A-37C are views for explaining the initialization processfor performing the spray-bend transition in the conventional liquidcrystal display, wherein FIG. 37A is a graph showing change in the rateof the spray-bend transition, and FIGS. 37B, 37C are graphs each showinga waveform of a voltage applied to the liquid crystal display panel inthe initialization process.

[0013] In FIG. 37A, a longitudinal axis indicates the rate of transitionfrom initial spray alignment to bend alignment in the liquid crystallayer included in the liquid crystal display panel. In FIGS. 37B, 37C,longitudinal axes respectively indicate potential difference between thesource line and the counter electrode and potential difference betweenthe gate line and the source line.

[0014] As shown in FIG. 37B, in the initialization process, apredetermined voltage is applied intermittently to the source line andthe counter electrode so that the potential difference between thesource line and the counter electrode becomes 10V or more. Also, asshown in FIG. 37C, a predetermined voltage is applied to the gate lineand the source line so that the potential difference between the gateline and the source line becomes 10V or more over the wholeinitialization process. As a result, as shown in FIG. 37A, the rate oftransition to the bend alignment is increased stepwise and thespray-bend transition is completed when the initialization process isterminated.

[0015] By the way, how the spray-bend transition takes place is observedand the observation result shows that a nucleus of the bend alignment isgenerated from a specific spot and grown. Hereinbelow, this nucleus isnamed “transition nucleus”.

[0016] Publication of Examined Patent Application No. Hei. 10-20284discloses a liquid crystal display panel in which a convex/concaveportion made of a conductive material is formed at a predeterminedposition on the side of an array substrate for the purpose of generatingthe transition nucleus. In this constitution, since the electric fieldstrength applied to a region of the liquid crystal layer on theconvex/concave portion becomes larger than that around the region, thegeneration of the transition nucleus is facilitated. Consequently, thespray-bend transition smoothly takes place.

[0017] However, in the conventional liquid crystal display, thespray-bend transition sometimes takes place with low reliability becauseof insufficient strength of the electric field. In this case, thespray-aligned region is locally left and becomes a luminescent spot,which is observed as dot defect.

SUMMARY OF THE INVENTION

[0018] The present invention is directed to solving the above-describedproblem and an object thereof is to provide a liquid crystal displaycapable of reliably performing spray-bend transition.

[0019] To solve the above-described problem, there is provided a liquidcrystal display comprising: a pair of opposed substrates; a liquidcrystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state, before an image isdisplayed; a first electrode provided on one of the pair of substrates;a second electrode provided so as to overlap with the first electrodewith an insulator interposed therebetween and disposed between the firstelectrode and the liquid crystal layer, the second electrode having alack portion in a region overlapping with the first electrode; and drivemeans for generating potential difference between the first electrodeand the second electrode to thereby perform the initialization process.

[0020] In this constitution, when the potential difference is generatedbetween the first electrode and the second electrode, the electric fieldstrength around the lack portion included in the second electrode islarger than the electric field strength in the other region. As aresult, the liquid crystal molecules around the lack portion become thetransition nucleus and transition of the alignment state of the liquidcrystal layer reliably takes place.

[0021] In the liquid crystal display, one of the pair of substrates maybe an array substrate having a plurality of pixel electrodes provided inmatrix; a plurality of gate lines and source lines arranged so as tocross each other; a plurality of switching devices provided ascorresponding to the respective pixel electrodes, for switching betweena conductive state and a non-conductive state between the pixelelectrodes and the source lines in accordance with a drive signalsupplied through the gate lines, and the other of the pair of substratesmay be an opposing substrate having a counter electrode opposed to thearray substrate.

[0022] The liquid crystal display may further comprise storage capacitorelectrodes overlapping with the pixel electrodes, and the firstelectrode may be the storage capacitor electrode and the secondelectrode may be the pixel electrode.

[0023] In the liquid crystal display, the first electrode may be thegate line and the second electrode may be the pixel electrode.

[0024] The liquid crystal display, may further comprise storagecapacitor electrodes overlapping with the pixel electrodes, and thefirst electrode may be the storage capacitor electrode and the secondelectrode may be the source line.

[0025] In the liquid crystal display, the first electrode may be thegate line and the second electrode may be the source line.

[0026] In the liquid crystal display, the first electrode may be thepixel electrode and the second electrode may be the gate line.

[0027] The liquid crystal display, may further comprise storagecapacitor electrodes overlapping with the pixel electrodes, and thefirst electrode may be the pixel electrode and the second electrode maybe the storage capacitor electrode.

[0028] In the liquid crystal display, the first electrode may be thesource line and the second electrode may be the gate line.

[0029] The liquid crystal display, may further comprise storagecapacitor electrodes overlapping with the pixel electrodes, and thefirst electrode may be the source line and the second electrode may bethe storage capacitor electrode.

[0030] The liquid crystal display, may further comprise: a thirdelectrode and a fourth electrode provided on one of the pair ofsubstrates on which the first and second electrodes are not provided, soas to overlap each other with an insulator interposed therebetween, thethird electrode may be disposed between the fourth electrode and theliquid crystal layer and has a lack portion in a region overlapping withthe fourth electrode, and the drive means may be adapted to generate thepotential difference between the third electrode and the fourthelectrode to perform the initialization process.

[0031] In this constitution, when the potential difference is generatedbetween the third electrode and the fourth electrode to performtransition of the alignment state of the liquid crystal layer, theelectric field strength around the lack portion included in the thirdelectrode is larger than the electric field strength in the otherregion. As a result, the liquid crystal molecules around the lackportion of the third electrode as well as the liquid crystal moleculesaround the lack portion of the second electrode, become transitionnucleuses. By thus generating the transition nucleuses on the sides ofboth substrates, the transition of the alignment state of the liquidcrystal layer can take place more reliably.

[0032] In the liquid crystal display, the lack portion may be anaperture provided in the second electrode.

[0033] In this case, the aperture may include a plurality ofstraight-line portions extending toward a position at which theseportions cross each other. Also, the aperture may be V-shaped, W-shaped,or X-shaped. Further, the aperture may be polygon-shaped.

[0034] In the liquid crystal display, the lack portion may be shaped toenable application of two-direction electric fields to the liquidcrystal layer. In this constitution, two types of, i.e., clockwise andcounterclockwise twist-aligned regions may be formed. Since elasticstrain energy is increased at a spot where these twist-aligned regionsare in contact with each other, the transition of the alignment state ofthe liquid crystal layer smoothly takes place.

[0035] In the liquid crystal display, the second electrode has anaperture including a portion which is 4 μm wide or less. In thisconstitution, the electric field strength around the aperture includedin the first electrode can be made larger.

[0036] In the liquid crystal display, the lack portion may be a cutoutportion provided in the second electrode. In this constitution, theliquid crystal molecules around the cutout portion become the transitionnucleus and the transition of the alignment state of the liquid crystallayer can take place reliably.

[0037] According to the present invention, there is also provided aliquid crystal display comprising: a pair of opposed substrates; aliquid crystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed; a first electrode and a second electrode formed on one of thepair of substrates so as to overlap each other with an insulatorinterposed therebetween; drive means for generating potential differencebetween the first electrode and the second electrode to perform theinitialization process; and convex portions respectively formed atopposed positions in the pair of the substrates such that the convexportions are protruded in the thickness direction of the liquid crystallayer.

[0038] In the constitution, the cell gap in the region with the convexportion is smaller than the cell gap in the region without the convexportion. Thereby, when the potential difference is generated between thefirst electrode and the second electrode to perform transition of thealignment state of the liquid crystal layer, the electric field strengthcan be locally increased around the cell gap in the region with theconvex portion. As a result, the liquid crystal molecules around thecell gap become the transition nucleus and the transition of thealignment state of the liquid crystal layer can reliably take place.

[0039] According to the present invention, there is still furtherprovided a liquid crystal display having: a pair of opposed substrates;and a liquid crystal layer disposed between the pair of substrates, theliquid crystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed; comprising: a first electrode provided on one of the pair ofsubstrates; a second electrode placed between the first electrode andthe liquid crystal layer; and drive means for generating potentialdifference between the first electrode and the second electrode tothereby perform the initialization process, and opposed end portions oftwo adjacent second electrodes overlap with the first electrode with aninsulator interposed therebetween.

[0040] In the constitution, when the potential difference is generatedbetween the first electrode and the second electrode to performtransition of the alignment state of the liquid crystal layer, theelectric field strength is locally increased between the opposed endportions of the adjacent second electrodes. As a result, the liquidcrystal molecules around the region between the opposed end portionsbecome transition nucleuses and the transition of the alignment state ofthe liquid crystal molecules can reliably take place.

[0041] In the liquid crystal display, one of the opposed end portionsmay have a protrusion in a region overlapping with the first electrodeand the other end portion may have a recess corresponding to theprotrusion in the region overlapping with the first electrode. In thisconstitution, the liquid crystal molecules around the region between theprotrusion and the corresponding recess become transition nucleus andthe transition of the alignment state of the liquid crystal layer canreliably take place.

[0042] In the liquid crystal display, distance between the protrusionand the recess may be 4 μm-8 μm. Thereby, without shorting between thefirst electrodes, the electric field strength between the protrusion andthe corresponding recess can be increased.

[0043] In the liquid crystal display, the protrusion may be saw-toothshaped.

[0044] In the liquid crystal display, one of the pair of substrates maybe an array substrate having a plurality of pixel electrodes provided inmatrix; a plurality of gate lines and source lines arranged so as tocross each other; a plurality of switching devices provided ascorresponding to the respective pixel electrodes, for switching betweena conductive state and a non-conductive state between the pixelelectrodes and the source lines in accordance with a drive signalsupplied through the gate lines, and the other of the pair of substratesmay be an opposing substrate having a counter electrode opposed to thearray substrate.

[0045] The liquid crystal display, may further comprise storagecapacitor electrodes overlapping with the pixel electrodes, and thefirst electrode may be the storage capacitor electrode and the secondelectrode may be the pixel electrode.

[0046] In the liquid crystal display, the first electrode may be thegate line and the second electrode may be the pixel electrode.

[0047] In the liquid crystal display, the insulator may be a colorfilter or a flattening layer. In this constitution, the color filter orthe flattening layer can be used as the insulator between the firstelectrode and the second electrode.

[0048] In the liquid crystal display, an intermediate portion may beformed between a main portion of the second electrode and the endportion of the second electrode so as to have a width smaller than awidth of the main portion and a width of the end portion.

[0049] In this constitution, by adjusting the width and length of theintermediate portion, the storage capacitance generated between theopposed end portions of the adjacent pixel regions and the storagecapacitance generated by the other elements can be well-balanced.

[0050] In the liquid crystal display, the first electrode may becomprised of a conductive mask and the second electrode may be thecounter electrode.

[0051] In the liquid crystal display, the potential difference ispreferably 15V-32V.

[0052] In the liquid crystal display, voltages of different polaritiesmay be respectively applied to adjacent pixel electrodes. Thus, byapplying the voltage by so-called dot inverting method, two-directiontransversal electric fields can be generated. As a result, two types of,i.e., clockwise or counterclockwise twist-aligned regions can be formed.Since the elastic strain energy is increased at the spot where thesetwist-aligned regions are in contact with each other, the transition ofthe alignment state of the liquid crystal layer can take place moresmoothly.

[0053] In the liquid crystal display, the non-display alignment statemay be spray alignment and the display alignment state may be bendalignment. Thereby, a liquid crystal display capable of reliablyperforming spray-bend transition is realized.

[0054] The liquid crystal display, may further comprise: an illuminatingdevice having a light source for emitting red light, green light, andblue light; and illuminating device control means for controlling theilluminating device so as to emit the red light, the green light and theblue light by time division within one frame period. Thereby, a liquidcrystal display that employs so-called field sequential color method andis capable of reliably performing transition of the alignment state ofthe liquid crystal layer can be realized.

[0055] According to the present invention, there is still furtherprovided a liquid crystal display comprising: a pair of opposedsubstrates; a liquid crystal layer disposed between the pair ofsubstrates, the liquid crystal layer having a display alignment stateand a non-display alignment state which differ from each other and beingsubjected to an initialization process so as to be changed from thenon-display alignment state to the display alignment state before animage is displayed, and one of the pair of substrates may be an arraysubstrate having a plurality of pixel electrodes provided in matrix; aplurality of gate lines and source lines arranged so as to cross eachother; a plurality of switching devices provided as corresponding to therespective pixel electrodes, for switching between a conductive stateand a non-conductive state between the pixel electrodes and the sourcelines in accordance with a drive signal supplied through the sourcelines, and the other of the pair of substrates may be an opposingsubstrate having a counter electrode opposed to the array substrate, anda source electrode constituting the switching device may extend from thesource line in parallel with the gate line so as to overlap with thegate line and may be interposed between the gate line and the liquidcrystal layer, and a drive signal for causing conduction between thepixel electrode and the source lines may be supplied to the gate linesto set the source electrode and the pixel electrodes at equipotentialand potential difference is generated between the source line and thegate line to thereby perform the initialization process.

[0056] In the liquid crystal display, potential difference may begenerated between the counter electrode and the pixel electrode.

[0057] In the liquid crystal display, the source electrode may have abent portion.

[0058] This object, as well as other objects, features and advantages ofthe invention will become more apparent to those skilled in the art fromthe following description taken with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0059]FIG. 1 is a cross-sectional view schematically showing aconstitution of a liquid crystal display panel included in a liquidcrystal display according to a first embodiment of the presentinvention;

[0060]FIG. 2 is a plan view schematically showing a constitution of mainelements of the liquid crystal display panel included in the liquidcrystal display according to the first embodiment;

[0061]FIG. 3 is a cross-sectional view taken in the direction of arrowssubstantially along line III-III of FIG. 2;

[0062]FIG. 4 is an enlarged view of a liquid crystal layer portion inthe cross section of FIG. 3;

[0063]FIG. 5 is a block diagram showing a constitution of the liquidcrystal display according to the first embodiment;

[0064]FIG. 6 is a graph showing the relationship between an appliedvoltage and Gibbs energy;

[0065]FIG. 7 is a view showing lines of equipotential of a cross sectionof a pixel in the liquid crystal display according to the firstembodiment;

[0066]FIG. 8 is a view showing distribution of the Gibbs energy in aplane of the pixel in the liquid crystal display according to the firstembodiment;

[0067]FIG. 9 is a view showing an example of waveforms of a transitionvoltage in the liquid crystal display according to the first embodiment;

[0068]FIG. 10 is a view showing another example of waveforms of thetransition voltage in the liquid crystal display according to the firstembodiment;

[0069]FIG. 11 is a view for explaining a dot inverting method;

[0070]FIG. 12 is a view for explaining a line inverting method;

[0071]FIG. 13 is a plan view schematically showing another constitutionof main elements of the liquid crystal display panel included in theliquid crystal display according to the first embodiment;

[0072]FIG. 14 is a plan view schematically showing still anotherconstitution of the main elements of the liquid crystal display panelincluded in the liquid crystal display according to the firstembodiment;

[0073]FIG. 15 is a plan view schematically showing a furtherconstitution of main elements of the liquid crystal display panelincluded in the liquid crystal display according to the firstembodiment;

[0074]FIG. 16 is a plan view schematically showing a still furtherconstitution of main elements of the liquid crystal display panelincluded in the liquid crystal display according to the firstembodiment;

[0075]FIG. 17 is a cross-sectional view schematically showing aconstitution of a liquid crystal display panel included in a liquidcrystal display according to a second embodiment of the presentinvention;

[0076]FIG. 18 is a cross-sectional view schematically showing aconstitution of a liquid crystal display panel included in a liquidcrystal display according to a third embodiment of the presentinvention;

[0077]FIG. 19 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a fourth embodiment of the presentinvention;

[0078]FIG. 20 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a fifth embodiment of the presentinvention;

[0079]FIG. 21 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a sixth embodiment of the presentinvention;

[0080]FIG. 22 is a cross-sectional view taken in the direction of arrowssubstantially along line XXII-XXII of FIG. 21;

[0081]FIG. 23 is a cross-sectional view schematically showing aconstitution of main elements of a liquid crystal display panel includedin a liquid crystal display according to a seventh embodiment of thepresent invention;

[0082]FIG. 24 is a cross-sectional view schematically showing aconstitution of main elements of a semiconductor switching device (TFT)portion of a liquid crystal display panel included in a liquid crystaldisplay according to an eighth embodiment of the present invention;

[0083]FIG. 25 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a ninth embodiment of the presentinvention;

[0084]FIG. 26 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a tenth embodiment of the presentinvention;

[0085]FIG. 27 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to an eleventh embodiment of the presentinvention;

[0086]FIG. 28 is a cross-sectional view taken in the direction of arrowssubstantially along line XXVIII-XXVIII of FIG. 27;

[0087]FIG. 29 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a twelfth embodiment of the presentinvention;

[0088]FIG. 30 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display according to a thirteenth embodiment of the presentinvention;

[0089]FIG. 31 is a cross-sectional view schematically showing aconstitution of a liquid crystal display according to a fourteenthembodiment of the present invention;

[0090]FIG. 32 is a plan view schematically showing a structure of apixel included in the liquid crystal display according to a fifteenthembodiment of the present invention;

[0091]FIG. 33 is a view showing an example of waveforms of a transitionvoltage in a liquid crystal display according to a fifteenth embodimentof the present invention;

[0092]FIG. 34 is a view showing another example of the waveforms of thetransition voltage in the liquid crystal display according to thefifteenth embodiment;

[0093]FIG. 35 is a view showing a further example of the waveforms ofthe transition voltage in the liquid crystal display according to thefifteenth embodiment;

[0094]FIG. 36 is a cross-sectional view schematically showing aconstitution of the conventional OCB-mode liquid crystal display panel;and

[0095] FIGS. 37A-37C are views for explaining an initialization processfor spray-bend transition in the conventional liquid crystal display,wherein

[0096]FIG. 37A is a graph showing change in the rate of the spray-bendtransition and

[0097]FIGS. 37B, C are graphs showing waveforms of voltages applied tothe liquid crystal display panel during the initialization process.

DETAILED DESCRIPTION OF THE PREFRRED EMBODIMENTS

[0098] Hereinafter, preferred embodiments of the present invention willbe described with reference to drawings.

[0099] (First Embodiment)

[0100] A first embodiment of the present invention embodies a liquidcrystal display capable of reliably performing spray-bend transition byproviding an aperture in a pixel electrode formed on an inner surface ofan array substrate.

[0101]FIG. 1 is a cross-sectional view schematically showing aconstitution of a liquid crystal display panel included in a liquidcrystal display according to a first embodiment of the presentinvention. In FIG. 1, for the sake of convenience, a direction indicatedby an arrow X indicates an upper side of the liquid crystal displaypanel.

[0102] Referring now to FIG. 1, a liquid crystal display panel 100included in the liquid crystal display of this embodiment has a liquidcrystal cell 101 described later. A retardation film (hereinafter simplyreferred to as a negative retardation film) 104 a comprised of anoptical medium having a negative refractive index anisotropy whose mainaxes are hybrid-arranged, a negative uniaxial retardation film 105 a, apositive uniaxial retardation film 106, and a polarizer 107 a aredisposed on an upper surface of the liquid crystal cell 101 in thisorder. A negative retardation film 104 b, a negative uniaxialretardation film 105 b, and a polarizer 107 b are disposed on a lowersurface of the liquid crystal cell 101. It should be noted that anegative retardation film 104 and a biaxial retardation film (notshown), and the polarizer may be disposed on each of the surfaces of theliquid crystal cell 101 in this order because the biaxial retardationfilm functions as both of the negative uniaxial retardation film and thepositive uniaxial retardation film.

[0103]FIG. 2 shows a plan view schematically showing a constitution ofthe liquid crystal cell 101. FIG. 3 is a cross-sectional view taken inthe direction of arrows substantially along line III-III of FIG. 2. FIG.4 is an enlarged view of a liquid crystal layer portion in the crosssection of FIG. 4. In FIG. 2, for the sake of convenience, elementsprovided above the pixel electrode are omitted.

[0104] Referring to FIGS. 2, 3, the liquid crystal cell 101 comprisestwo substrates, namely, a color filter substrate 102 including a colorfilter described later and an array substrate 103. The color filtersubstrate 102 and the array substrate 103 are provided as opposed toeach other with a spacer (not shown) interposed therebetween and aliquid crystal layer 4 is provided in a gap between the color filtersubstrate 102 and the array substrate 103. The liquid crystal layer 4contains liquid crystal molecules 20 filled thereinto as described withreference to FIG. 4. The liquid crystal molecules 20 are made of acyano-based liquid crystal material having refractive index anisotropyΔn of 0.2 or more in order to increase Gibbs energy described later.

[0105] The color filter substrate 102 is structured such that a colorfilter layer 21, a transparent electrode (counter electrode) 2, and analignment layer 3 are disposed on the lower surface of the glasssubstrate 1. The color filter layer 21 is comprised of a red colorfilter 21R, a green color filter 21G, and a blue color filter 21B. Blackmatrixes 22 as masks are respectively provided at boundaries of thecolor filters.

[0106] The array substrate 103 has a glass substrate 10 and a wiringlayer 17 is formed on an upper surface of the glass substrate 10. Thewiring layer 17 is comprised of gate lines 12 and source lines 11crossing each other, storage capacitor electrodes 9, and an insulatorfor preventing conduction between these electrodes. To be more detailed,the storage capacitor electrodes 9 are each formed in parallel with thegate lines 12 so as to be placed at a predetermined position between thegate lines 12. The gate lines 12 and the storage capacitor electrodes 9are formed in the same layer as a lowermost layer. An insulating layer 8covers the gate lines 12 and the storage capacitor electrodes 9. Thesource lines 11 are formed on the upper surface of the insulating layer8 and an insulating layer 7 covers the source lines 11.

[0107] Pixel electrodes 6 are each formed on the upper surface of thewiring layer 17 so as to be located in a pixel region defined by thegate lines 12 and the source lines 11. Since the storage capacitorelectrode 9 is provided between the gate lines 12 as described above,the pixel electrode 6 has a region overlapping with the storagecapacitor electrode 9 with the insulating layers 7, 8 interposedtherebetween. The overlapping region has a rectangular aperture 6 a.

[0108] An alignment layer 5 covers the pixel electrodes 6 and the wiringlayer 17. The alignment layer 5 and the alignment layer 3 provided onthe side of the color filter 102 have been subjected to alignmenttreatment such as known rubbing treatment in order to align the liquidcrystal molecules in the liquid crystal layer 4 in parallel with oneanother and in the same direction. Here, it is assumed that thedirection of the alignment treatment is parallel to the source lines 11.

[0109] Reference 13 denotes TFTs (Thin Film Transistor) as asemiconductor switching device and reference 14 denotes drain electrodesconnecting the TFTs 13 and the pixel electrodes 6.

[0110] In an initial state of the liquid crystal display panel 100 soconstituted, the liquid crystal molecules 20 have spray alignment shownin FIG. 4A. In the liquid crystal display of this embodiment, byapplying a certain voltage to the liquid crystal display panel 100 asdescribed later, the liquid crystal molecules 20 are caused totransition from spray alignment to bend alignment of FIG. 4B. In thisbend alignment state, an image is displayed in the liquid crystaldisplay. In brief, the liquid crystal display panel 100 is an OCB-modedisplay panel. Hereinbelow, the voltage applied to the liquid crystaldisplay panel 100 in the spray-bend transition is referred to as atransition voltage.

[0111]FIG. 5 is a block diagram showing a constitution of the liquidcrystal display according to the first embodiment. Referring to FIGS. 5,2, 3, the liquid crystal display panel 100 is a well-known TFT (ThinFilm Transistor) type liquid crystal display panel in which the gatelines 12 and the source lines 11 are provided in matrix. In the liquidcrystal display panel 100, the gate lines 12 and the sources line 11 arerespectively driven by a gate driver 502 and a source driver 503 whichare controlled by a control circuit 501.

[0112] A backlight 500 is provided below the liquid crystal displaypanel 100. The backlight 500 is composed of a cathode ray tube or thelike for emitting white light.

[0113] In the liquid crystal display of this embodiment so constituted,the control circuit 501 outputs control signals to the gate driver 502and the source driver 503, respectively, according to a video signal 504externally input. Thereby, the gate driver 502 applies a scanning signalvoltage to the gate lines 12, thereby causing the TFTs 13 of therespective pixels to be sequentially turned on, and according to thistiming, the source driver 503 sequentially applies a video signalvoltage according to the video signal 504 to the pixel electrodes 6 ofthe pixels through the source lines 11. Thereby, the liquid crystalmolecules are modulated and light transmittance of light emitted fromthe backlight 500 changes. As a result, an image according to the videosignal 504 is presented to an observer.

[0114] Subsequently, the spray-bend transition in the liquid crystaldisplay of this embodiment so constituted will be described in detail.

[0115]FIG. 6 is a graph showing the relationship between an appliedvoltage and Gibbs energy. Here, the Gibbs energy refers to the sum ofelectric energy and elastic energy.

[0116] In FIG. 6, reference numeral 31 indicates applied voltage—Gibbsenergy characteristic in the case where the liquid crystal molecules arein the bend alignment state and reference numerals 32, 33 respectivelyindicate applied voltage-Gibbs energy characteristics in the case wherethe liquid crystal molecules are in twist alignment and spray alignmentstates.

[0117] Referring to FIG. 6, when the applied voltage is lower than acritical voltage Vcr, the Gibbs energy of the liquid crystal moleculesin the spray alignment is lower than that of the liquid crystalmolecules in the bend alignment. The event that the Gibbs energy is lowis equivalent to the event that a negative energy is high, andtherefore, indicates a more stable state. In this case, therefore, thespray alignment is more stable than bend alignment.

[0118] This relationship is reversed when the applied voltage is higherthan the critical voltage Vcr, and the Gibbs energy in the bendalignment state is lower than that in the spray alignment state. Thismeans that the bend alignment is more stable than spray alignment.

[0119] When a relatively high voltage is applied, the liquid crystalmolecules tend to transition to the bend alignment which are more stablethan the spray alignment. So, when there is a spot where an electricfield strength is locally high, the liquid crystal molecules around thespot transition to the bend alignment and such transition spreads to theother liquid crystal molecules. In other words, the liquid crystalmolecules around the spot where the electric field strength is locallyhigh becomes the transition nucleus and the spray-bend transition takesplace.

[0120] In the liquid crystal display of this embodiment, the liquidcrystal molecules around the aperture 6 a formed in the pixel electrode6 become the transition nucleus. Hereinafter, this will be explained.

[0121] For the purpose of measuring electric field distribution in thevicinity of the aperture 6 a of the pixel electrode 6, an electric fieldsimulation is carried out in the liquid crystal display of thisembodiment. Specifically, +7V voltage and a −25V voltage arerespectively applied to the pixel electrode 6 and the storage capacitorelectrode 9 and change in the electric field strength is observed. Here,the aperture 6 a is rectangle which is 4 μm wide and 8 μm long.

[0122]FIGS. 7. 8 are views showing a result of the electric fieldsimulation. FIG. 7 shows equipotential lines of a cross section of anarbitrary pixel in the liquid crystal display of this embodiment andFIG. 8 shows distribution of Gibbs energy on a plane of the pixel. InFIG. 8, a denser region represents that negative energy is higher (Gibbsenergy is lower).

[0123] As shown in FIG. 7, the equipotential lines are dense around theaperture 6 a. This shows that the electric field strength is locallyhigh around the aperture 6 a, that is, electric field concentrationoccurs. This is due to the fact that the aperture 6 a is provided in theregion where the pixel electrode 6 overlaps with the storage capacitorelectrode 9 and different voltages are applied to the pixel electrode 6and the storage capacitor electrode 9. As can be seen from FIG. 8, thenegative energy is high around the aperture 6 a. It was confirmed thatthe spray-bend transition is facilitated around the aperture 6 a. Thatis, it was found that the liquid crystal molecules around the aperture 6a become the transition nucleus.

[0124] As described above, in the liquid crystal display, each of thepixel electrodes 6 has the aperture 6 a. This means that the transitionnucleus is present in each pixel. Consequently, pixels in the sprayalignment state are not left and the spray-bend transition reliablytakes place.

[0125] Subsequently, waveforms of the transition voltage in the liquidcrystal display of this embodiment and a method for applying thetransition voltage will be explained.

[0126]FIG. 9 is a view showing waveforms of the transition voltage inthe liquid crystal display of this embodiment. In the liquid crystaldisplay of this embodiment, as shown in FIG. 9, an AC rectangular wavevoltage input to respective pixel electrodes 6Aa, 6Cc . . . throughsource lines 11A, 11C . . . on odd columns and an AC rectangular wavevoltage input to respective pixel electrodes 6Bb, 6Dd . . . throughsource lines 11B, 11D . . . on even columns are reversed in polarity.

[0127] In this case, first of all, +15V voltage as a drive signal isapplied to the gate line 12 a on a first row, thereby causingsequentially TFTs 13Aa, 13Ab, 13Ac, . . . of the pixel electrodes 6Aa,6Ab, 6Ac . . . on the first row to be sequentially turned on. When theTFTs 13Aa, 13Ab, 13Ac . . . are turned on, +7V voltage is being appliedto the source lines 11A, 11C . . . , as shown in FIG. 9. Thereby, +7Vvoltage is applied from the source lines 11A, 11C . . . to the pixelelectrodes 6Aa, 6Ac . . . , through the TFTs 13Aa, 13Ac . . . ,respectively. Likewise, when the TFTs 13Aa, 13Ab, 13Ac . . . are turnedon, −7V voltage is being applied to the source lines 11B, 11D . . . .Thereby, −7V voltage is applied from the source lines 11B, 11D . . . tothe pixel electrodes 6Ab, 6Ad . . . , through the TFTs 13Ab, 13Ad . . ., respectively.

[0128] Then, −15V voltage is applied to the gate line 12 a on the firstrow, thereby causing the TFTs 13Aa, 13Ab, 13Ac . . . of the pixelelectrodes 6Aa, 6Ab, 6Ac on the first row to be sequentially turned off.Simultaneously, +15V voltage is applied to the gate line 12 b on thesecond row, thereby causing the TFTs 13Ba, 13Bb, 13Bc . . . of the pixelelectrodes 6Ba, 6Bb, 6Bc on the second row to be sequentially turned on.When the TFTs 13Ba, 13Bb, 13Bc . . . are turned on, −7V voltage is beingapplied to the source lines 11A, 11C . . . , as shown in FIG. 9.Therefore, −7V voltage is applied from the source lines 11A, 11C . . .to the pixel electrodes 6Ba, 6Bc . . . , through the TFTs 13Ba, 13Bc . .. , respectively. Likewise, when the TFTs 13Ba, 13Bb, 13Bc . . . areturned on, +7V voltage is being applied to the source lines 11B, 11D . .. . Therefore, +7V voltage is applied from the source lines 11B, 11D . .. to the pixel electrodes 6Bb, 6Bd through the TFTs 13Bb, 13Bd . . . ,respectively.

[0129] By applying the AC rectangular wave voltage to the respectivepixel electrodes 6 from the source lines 11 by sequentially applying+15v voltage to all the gate lines 12, the plus voltage is applied tothe pixel electrodes 6Aa, 6Ca, 6Ac, 6Cc . . . . on the odd rows andcolumns and the pixel electrodes 6Bb, 6Db, 6Bd, 6Dd . . . on the evenrows and columns, while the minus voltage is applied to the pixelelectrodes 6Ba, 6Da, 6Bc, 6Dc . . . on the even rows and odd columns andthe pixel electrodes 6Ab, 6Cb, 6Ad, 6Cd . . . on the odd rows and evencolumns.

[0130] Thereby, the electric field is generated between each of thepixel electrodes 6Aa, 6Ba, 6Ca, 6Da . . . on the odd columns and each ofthe pixel electrodes 6Ab, 6Bb, 6Cb, 6Db . . . on the even rows, as wellas between each of the pixel electrodes 6Aa, 6Ca . . . on odd rows andeach of the pixel electrodes 6Ba, 6Da . . . on even rows, which is shownin FIG. 11.

[0131] When the dot inverting method in which the voltage polarity isreversed for every dot, a transversal electric field which is parallelto the substrate is generated in each pixel. The transverse electricfield has two directions respectively indicated by arrows 110, 120(length direction of the source line 11 and length direction of the gateline 12). For this reason, two types of, i.e., clockwise andcounterclockwise, twist-aligned regions are formed. Around a spot wherethese twist-aligned regions are in contact with each other, elasticstrain energy is increased, which results in increased negative energy.This facilitates the spray-bend transition.

[0132] While the voltage is being applied to the pixel electrodes 6 inthe above-described manner, −25V voltage is applied to the counterelectrode 2 and the storage capacitor electrode 9 for one second asshown in FIG. 9.

[0133] By applying the transition voltage, the potential difference inthe thickness direction of the liquid crystal display panel 100 isincreased. Since the pixel electrode 6 has the aperture 6 a in theregion overlapping with the storage capacitor electrode 9 with theinsulator interposed therebetween, the increase in the potentialdifference in the thickness direction of the liquid crystal displaypanel causes the strong electric field concentration to occur around theaperture 6 a. As a result, the liquid crystal molecules around theaperture 6 a formed in each pixel electrode 6 become the transitionnucleus and the spray bend transition reliably takes place.

[0134] The counter electrode 2 and the storage capacitor electrode 9 maybe shorted in structure. The voltage is not necessarily sequentiallyapplied to the respective gate lines 12 but a gate-on potential may becontinuously applied thereto during the initialization process.

[0135] While the potential difference generated between the counterelectrode 2 and the pixel electrode 6 by respectively applying −25V, 7Vvoltages to these electrodes, is 32V at maximum, another values, i.e.,values sufficient to generate the transition nucleus may be adopted.Specifically, the voltage is approximately 10-35V and preferably 15-32V.

[0136] The transition voltage having the waveforms of FIG. 10 may beemployed. In this case, differently from the case of FIG. 9, no voltageis applied to the pixel electrodes 6 by keeping the source lines 11 atpotential of 0 V and −25 V voltage is applied to the counter electrode 2and the storage capacitor electrode 9 for one second. Also in this case,the spray-bend transition reliably takes place as in the case of usingthe transition voltage of the waveforms of FIG. 9.

[0137] In some cases where the voltage is being applied to the liquidcrystal layer 4, i.e., across the pixel electrode 6 and the counterelectrode 2, before the transition voltage is applied, the spray bendtransition does not smoothly take place due to formation of the sprayalignment with the liquid crystal molecules arranged asymmetrically. Itis therefore desirable that no voltage is applied across the pixelelectrode 6 and the counter electrode 2 just before application of thetransition voltage. Thereby, since the spray alignment with the liquidcrystal molecules arranged symmetrically can be maintained withoutapplication of the voltage to the liquid crystal layer 4, the transitionto the bend alignment smoothly takes place.

[0138] Instead of the dot inverting method, the transition voltage maybe applied according to the line inverting method in which the voltagepolarity is reversed for every line. In this case, one-direction(indicated by arrow 110) transversal electric field is generated andfacilitates the spray-bend transition.

[0139] While the aperture 6 a of the pixel electrode 6 is rectangular inthe liquid crystal display according to the embodiment as describedabove, another shapes described below may be adopted.

[0140]FIGS. 13 through 16 are plan views showing the another shapes ofthe aperture 6 a of the pixel electrode 6. The aperture 6 a of the pixelelectrode 6 of FIG. 13 is comprised of two straight-line portionsextending toward a position at which these portions cross each other.The one end portions of the straight-line portions are in contact witheach other, thereby forming an inverted-V shape. This shape is capableof generating two-direction transversal electric fields and therebyforming two types of clockwise and counterclockwise twist-alignedregions. As a result, at the spot where these twist-aligned regions arein contact with each other, the elastic strain energy, and hence, thenegative energy are increased. By locally increasing the negativeenergy, the liquid crystal molecules around the aperture 6 a become thetransition nucleus and the spray-bend transition smoothly takes place.

[0141] Instead of the inverted V-shape, the shape obtained by rotatingthe inverted V-shape in multiples of 90 degrees, including V-shape, maybe adopted. With such shapes, the two types of twist-aligned regions canalso be formed.

[0142] The aperture 6 a of the pixel electrode 6 of FIG. 14 is of aninverted-W shape with two continuous inverted V shapes. With this shape,the two types of twist-aligned regions can be formed.

[0143] Instead of the inverted-W shape, it is needless to say that theshape obtained by rotating the inverted-W shape in multiples of 90degrees, may be adopted. Three or more continuous inverted-V shapes maybe adopted.

[0144] The aperture 6 a of the pixel electrode 6 of FIG. 15 is comprisedof two straight-line portions as in the case of FIG. 13 and is X-shapedin which their central portions cross each other. With this shape, thetwo types of twist-aligned regions can also be formed.

[0145] The aperture 6 a of the pixel electrode 6 of FIG. 16 is of arhombus shape. Other than the rhombus, polygons such as a triangle and aparallelogram, may be adopted. With such shapes, the two types oftwist-aligned regions can also be formed.

[0146] The aperture 6 a of the pixel electrode 6 may be of various typesof shapes as described above and a width and size thereof are notuniquely determined. Nevertheless, it is preferable that the width isrelatively small for the purpose of generating stronger electric fieldconcentration. Specifically, the aperture 6 a preferably has a portionof 4 μm wide or less.

[0147] (Second Embodiment)

[0148] A second embodiment of the present invention illustrates a liquidcrystal display provided with a flattening layer 18.

[0149] The source lines 11 are each provided between the pixelelectrodes 6 in the liquid crystal display of the first embodiment asshown in FIG. 2, and part of the first insulating layer 7 forms a convexportion between the pixel electrodes 6 as corresponding to the thicknessof the source line 11. For this reason, the distance between the pixelelectrodes 6 needs to be greater than the width of the convex portionand as a result, an aperture ratio is reduced. Accordingly, in thisembodiment, the flattening layer 18 is provided as described below.

[0150]FIG. 17 is a cross-sectional view schematically showing aconstitution of the liquid crystal display panel included in the liquidcrystal display of this embodiment. As shown in FIG. 17, the flatteninglayer 18 made of a resin material such as acryl-based resist covers thesurface of the first insulating layer 7 and the pixel electrodes 6 areformed on the flattening layer 18.

[0151] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals and as such, will not be described herein.

[0152] The provision of the flattening layer 18 can reduce the distancebetween the pixel electrodes 6. This can increase the aperture ratio,and therefore, sufficiently bright display is achieved with powerconsumption reduced.

[0153] The flattening layer 18 not only serves to flatten unevenness ofthe layer but also serves as an insulator between the pixel electrode 6and the storage capacitor electrode 9.

[0154] (Third Embodiment)

[0155] A third embodiment of the present invention illustrates a liquidcrystal display in which the color filter layer is formed on the side ofthe array substrate.

[0156]FIG. 18 is a cross-sectional view schematically showing aconstitution of a liquid crystal display panel included in a liquidcrystal display of this embodiment. As shown in FIG. 18, a color filterlayer 21 comprised of color filters 21R, 21G, 21B and black matrixes 22provided between the filter 21R and the filter 21G and between thefilter 21G and the filter 21B is formed on the insulating layer 7provided on the side of the array substrate 103.

[0157] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals and as such, will not be described herein.

[0158] In this constitution, the color filter layer 21 not onlyfunctions as the insulator between the pixel electrodes 6 and thestorage capacitor electrode 9 but also a filter for color display.

[0159] (Fourth Embodiment)

[0160] A fourth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray bend transition byproviding apertures in the pixel electrode and the source line formed onthe inner surface of the array substrate.

[0161]FIG. 19 is a plan view schematically showing a constitution of aliquid crystal display panel included in the liquid crystal display ofthis embodiment. As shown in FIG. 19, parts of opposite end portions ofthe pixel electrode 6 are respectively protruded toward thecorresponding gate lines 12 so as to overlap with the gate lines 12. Thepixel electrode 6 has rectangular apertures 6 a provided in regions ofthe protruded portions which overlap with the gate lines 12. In additionto these apertures 6 a, the pixel electrode 6 has a rectangular aperture6 a provided in the region overlapping with the storage capacitorelectrode 9, similar to the first embodiment. The pixel electrode 6overlaps with the gate lines 12 and the storage capacitance electrode 9with the insulating layer interposed therebetween, similarly to thefirst embodiment.

[0162] The source line 11 overlaps with the gate line 12 with theinsulating layer interposed therebetween, and the rectangular aperture11 a is provided in the overlapping region.

[0163] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereferences, and as such, will not be described.

[0164] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, thepotential difference in the thickness direction of the liquid crystaldisplay panel is increased. Since the pixel electrode 6 has theapertures 6 a in the regions overlapping with the gate lines 12 and thestorage capacitor electrode 9 with the insulating layer interposedtherebetween as described above, the increase in the potentialdifference in the thickness direction of the liquid crystal displaypanel causes the strong electric field concentration to occur around therespective apertures 6 a. As a result, the liquid crystal moleculesaround the apertures 6 a become the transition nucleus and thespray-bend transition smoothly takes place.

[0165] Likewise, when the transition voltage is applied to the sourcelines 11 and the gate lines 12, the potential difference in thethickness of the liquid crystal display panel is increased. Since thesource line 11 has the aperture 11 a in the region overlapping with thegate line 12 with the insulating layer interposed therebetween asdescribed above, the increase in the potential difference in thethickness direction of the liquid crystal display panel causes theelectric field concentration to occur around the aperture 11 a. As aresult, the liquid crystal molecules around the aperture 11 a become thetransition nucleus and the spray bend transition smoothly takes place.

[0166] Similarly to the first embodiment, the width of the aperture 6 aand the width of the aperture 11 a are respectively set to 4 μm or less.Thereby, stronger field electric field concentration occurs. Theapertures 6 a, 11 a need not be rectangular but may be of shapes ofFIGS. 12 through 15.

[0167] Thus, in this embodiment, the pixel electrode 6 has the pluralityof apertures 6 a and the source line 11 has the aperture 11 a. Since theliquid crystal molecules around the apertures 6 a, 11 a become thetransition nucleuses, the number of transition nucleuses is greater thanthat of the first embodiment. Consequently, the spray-bend transitiontakes place more reliably than that of the first embodiment.

[0168] (Fifth Embodiment)

[0169] A fifth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray-bend transition byproviding cutout portions in the pixel electrode formed on the innersurface of the array substrate.

[0170]FIG. 20 is a plan view schematically showing a constitution of aliquid crystal display panel included in a liquid crystal display ofthis embodiment. As shown in FIG. 20, parts of opposite end portions ofthe pixel electrode 6 are respectively protruded toward thecorresponding gate lines 12 so as to overlap with the gate lines 12. Aplurality of cutout portions 6 b are formed in the regions of theprotruded portions which overlap with the gate lines 12. Hence, theprotruded portions are comb-shaped. The width of these cutout portionsis 4 μm or less.

[0171] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals and as such will not be described herein.

[0172] When the transition voltage of the first embodiment is applied inthe liquid crystal display panel so constituted, the potentialdifference in the thickness direction of the liquid crystal displaypanel is increased. Since the pixel electrode 6 has the cutout portions6 b in the regions overlapping with the gate lines 12, the increase inthe potential difference in the thickness direction of the liquidcrystal display panel causes the strong electric field to occur aroundthe respective cutout portions 6 b. As a result, the liquid crystalmolecules around the cutout portions 6 b become the transition nucleusesand the spray-bend transition smoothly takes place.

[0173] The pixel electrode 6 may be provided with apertures in theregions overlapping with storage capacitor electrode 9, although suchapertures are not provided in this embodiment. Further, similarly to thefourth embodiment, the source line 11 may be provided with the aperturein the region overlapping with the gate line 12.

[0174] While the plurality of cutout portions 6 b are formed at the endportions of the pixel electrode 6, one aperture may be provided.

[0175] (Sixth Embodiment)

[0176] A sixth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray-bend transition byproviding cutout portions in the storage capacitor electrode and thegate line formed on the inner surface of the array substrate.

[0177]FIG. 21 is a plan view schematically showing a constitution of aliquid crystal display panel included in a liquid crystal display ofthis embodiment. FIG. 22 is a view taken in the direction of arrowssubstantially along line XXII-XXII of FIG. 20. In FIG. 22, for the sakeof convenience, elements provided above the storage capacitor electrodeare omitted.

[0178] Referring to FIGS. 21, 22, the liquid crystal cell 101 comprisesthe color filter 102 and the array substrate 103 which are opposed toeach other with a spacer (not shown) interposed therebetween. Since thecolor filter 102 is constituted similarly to that of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals, and as such, will not be described herein.

[0179] The array substrate 103 has the glass substrate 10. The pixelelectrodes 6 are formed on the upper surface of the glass substrate 10and the insulating layer 19 covers the pixel electrodes 6.

[0180] A wiring layer 25 is formed on the upper surface of theinsulating layer 19. The wiring layer 25 is comprised of the gate lines12 and the source lines 11 arranged to cross each other, the storagecapacitor electrodes 9, and the insulator for preventing the conductionbetween these electrodes. To be more detailed, the source lines 11 areformed on the insulating layer 19 and the insulating layer 7 covers thesource lines 11. The gate lines 12 and the storage capacitor electrodes9 are formed on the insulating layer 7 and the alignment layer 5 coversthe gate lines 12 and the storage capacitor electrodes 9.

[0181] Similarly to the first embodiment, the storage capacitorelectrode 9 is placed between the gate lines 12 and the pixel electrode6 is provided in the pixel region defined by the gate lines 12 and thesource lines 11. Therefore, the storage capacitor electrode 9 has theregion overlapping with the pixel electrode 6 with the insulating layers7, 19 interposed therebetween. A plurality of cutout portions 9 b areformed in the overlapping region.

[0182] Parts of opposite end portions of the pixel electrode 6 arerespectively protruded toward the corresponding gate lines 12 so as tooverlap with the gate lines 12. The gate lines 12 are provided with aplurality of cutout portions 12 b in the regions overlapping with theprotruded portion of the pixel electrode 6.

[0183] The width of these cutout portions 9 b, 12 b is 4 μm or less,similarly to the first embodiment.

[0184] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals, and as such will not be described herein.

[0185] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, thepotential difference in the thickness direction of the liquid crystaldisplay panel is increased. Since the storage capacitor electrode 9 hasthe cutout portions 9 b in the regions overlapping with the pixelelectrode 6 and the gate line 12 has the cutout portions 12 b, theincrease in the potential difference in the thickness direction of theliquid crystal display panel causes the strong electric fieldconcentration to occur around the cutout portions 9 b, 12 b. As aresult, the spray-bend transition smoothly takes place and asatisfactory image display without dot defect is obtained.

[0186] While the gate lines 12 and the storage capacitor electrode 9have the cutout portions only in the regions overlapping with the pixelelectrode 6, the cutout portions may be provided in the regionsoverlapping with the source line 11. Moreover, the cutout portions maybe replaced by apertures.

[0187] (Seventh Embodiment)

[0188] In the first through sixth embodiments, the apertures or cutoutportions are provided in the electrodes formed on the inner surface ofthe array substrate. On the other hand, a seventh embodiment of thepresent invention illustrates a liquid crystal display capable ofreliably performing spray-bend transition by providing apertures in anauxiliary electrode formed on the inner surface of an opposing substrate(color filter substrate).

[0189]FIG. 23 is a cross-sectional view schematically showing mainelements of a liquid crystal display panel included in a liquid crystaldisplay according to this embodiment. Referring to FIG. 23, the liquidcrystal cell 101 comprises the color filter substrate 102 and the arraysubstrate 103 which are opposed to each other with the spacer (notshown) interposed therebetween. Since the array substrate 103 isconstituted similarly to that of the first embodiment, the same orcorresponding parts are denoted by the same reference numerals, and assuch will not be described herein.

[0190] Auxiliary electrodes 51 are formed on the lower surface of thecounter electrode 2 formed on the inner surface of the color filtersubstrate 102 with an insulating layer 52 interposed therebetween. Theauxiliary electrodes 51 have substantially the same shape as the pixelelectrodes 6 formed on the inner surface of the array substrate 103 andare each located in the pixel region defined by the gate lines 12 andthe source lines 11, similarly to the pixel electrode 6. The alignmentlayer 3 covers the auxiliary electrodes 51 and the insulating layer 52.

[0191] As described above, since the auxiliary electrodes 51 havesubstantially the same shape as the pixel electrodes 6 and are providedwith a rectangular aperture 51 a 4 μm wide or less in the vicinity ofthe center thereof. The entire surface of the auxiliary electrode 51overlaps with the counter electrode 2, and hence, the aperture 51 a isformed in the region overlapping with the counter electrode 2. The shapeof the aperture 51 a is not limited to a rectangle but may adopt shapesshown in FIGS. 12 through 15, as described in the first embodiment.

[0192] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals and as such will not be described herein.

[0193] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, thepotential difference in the thickness direction of the liquid crystaldisplay panel is increased. Since the auxiliary electrode 51 has theaperture 51 a in the region overlapping with the counter electrode 2with the insulator interposed therebetween, the potential difference inthe thickness direction of the liquid crystal display panel isincreased. In addition, by applying a voltage different from thatapplied to the counter electrode 2 to the auxiliary electrodes 51, thestrong electric field concentration to occur around each of theapertures 51 a. As a result, the liquid crystal molecules around theapertures 51 a become the transition nucleuses and spray-bend transitionsmoothly takes place.

[0194] Since the auxiliary electrode 51 is provided in each pixel in theliquid crystal display of this embodiment, the transition nucleus ispresent in each pixel. Consequently, a satisfactory image displaywithout residual spray-aligned pixels is obtained.

[0195] Further, by generating the transition nucleuses on the side ofthe opposing substrate (color filter substrate), more transitionnucleuses can be generated. Consequently, the reliability of thespray-bend transition is further improved.

[0196] (Eighth Embodiment)

[0197] An eighth embodiment of the present invention illustrates aliquid crystal display capable of reliably performing spray bendtransition by providing protrusions on opposite portions of the arraysubstrate and the opposing substrate.

[0198]FIG. 24 is a cross-sectional view schematically showing mainelements of a semiconductor switching device (TFT) portion of a liquidcrystal display panel included in a liquid crystal display of thisembodiment. Referring to FIG. 24, the liquid crystal cell 101 comprisesthe color filter 102 and the array substrate 103 including thesemiconductor switching device TFT 13, which are opposed to each otherwith the spacer (not shown) interposed therebetween.

[0199] The array substrate 103 has the glass substrate 10. The gate line12 is formed on the upper surface of the glass substrate 10 and aninsulating layer 65 covers the gate line 12. The TFT 13 and the pixelelectrode 6 are formed on the upper surface of the insulating layer 65.

[0200] The TFT 13 is provided at a position corresponding to the gateline 12. The TFT 13 is structured such that a N⁺ a-Si layer 63 is formedon an active semiconductor layer 64 made of amorphous silicon (a-Si).The N⁺ a-Si layer 63 serves to electrically connect the activesemiconductor layer 64, and a source electrode 111 and a drain electrode14. As defined herein, the source electrode 111 refers to an electrodeconnected to the source line through which a signal voltage is suppliedthereto. The TFT 13 is protected by a protection film 62.

[0201] The color filter substrate 102 is structured such that the glasssubstrate 1, the color filter layer 21, the transparent electrode(counter electrode)2, and the alignment layer 3 are disposed in thisorder. The color filter layer 21 is composed of red, green, blue colorfilters and black matrixes at boundaries of these color filters.

[0202] A convex portion 66 protruded toward the array substrate 103 isformed on the lower surface of the counter electrode 2 as opposed to theTFT 13. The convex portion 66 is made of epoxy-based photosensitiveresin so as to have a suitable size. A cell gap 4 b between the colorfilter substrate 102 with the convex portion 66 and the array substrate103 with the TFT 13 is smaller than a cell gap 4 a between the colorfilter substrate 102 without the TFT 13 and the array substrate 103without the convex portion 66.

[0203] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, theelectric field concentration occurs around the cell gap 4 b. Thereby,the liquid crystal molecules around the cell gap 4 b become transitionnucleus and the spray-bend transition reliably takes place.Consequently, a high-quality liquid crystal display capable of providinga satisfactory image without dot defect is obtained.

[0204] While a narrow cell gap is formed by using the convex portion 66of the color filter substrate 102 and the TFT 13 of the array substrate103, the present invention is not limited to such constitution. As analternative, the narrow cell gap may be formed by providing a convexportion different from the TFT 13 on the array substrate 103 and anotherconvex portion on the color filter substrate 102 as opposed to theconvex portion different from the TFT 13.

[0205] (Ninth Embodiment)

[0206] A ninth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray-bend transition byproviding cutout portions in opposed end portions of adjacent pixelelectrodes formed on the inner surface of the array substrate.

[0207]FIG. 25 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display of this embodiment. Hereinbelow, for the sake ofconvenience, a pixel electrode 6A and a pixel electrode 6B adjacent tothe pixel electrode 6A in the length direction of the source line 11 arediscussed.

[0208] Referring to FIG. 25, the pixel electrode 6A overlaps with thegate lines 12 at end portions where a plurality of protrusions 6 cextended in the length direction of the source line 11 are formed. Endportions of the pixel electrode 6B which are opposed to the end portionswhere the protrusions 6 c are provided are protruded toward the gateline 12 so as to overlap with the gate line 12. Recesses 6 dcorresponding to the plurality of protrusions 6 c are formed in theregion of the protruded portion of the pixel electrode 6B which overlapswith the gate line 12.

[0209] Similarly to the first embodiment, the pixel electrode 6 overlapswith the gate lines 12 with the insulating layer interposedtherebetween.

[0210] Since the other elements are identical to those of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals and as such will not be described herein.

[0211] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, thepotential difference in the thickness direction of the liquid crystaldisplay panel is increased. Since the protrusions 6 c and thecorresponding recesses 6 d overlap with the gate line 12, the electricfield concentration occurs between protrusion 6 c and the correspondingrecess 6 d. As a result, the liquid crystal molecules in the regionbetween the protrusions 6 c and the recesses 6 d become the transitionnucleus and the spray-bend transition reliably takes place.Consequently, a high-quality liquid crystal display capable of providinga satisfactory image without dot defect is obtained.

[0212] In the ninth embodiment, if the voltages applied to the adjacentpixel electrodes 6A, 6B are reversed in polarity, for example, a pluspolarity voltage is applied to the pixel electrode 6A and a minuspolarity voltage is applied to the pixel electrode 6B, two-directiontransversal electric fields seen in a plan view are generated betweenthe adjacent pixel electrodes 6A, 6B, as indicated by arrows 110, 120.In this state, similarly to the description with reference to FIG. 11,the elastic strain energy of the liquid crystal molecules, and hence thenegative energy of the liquid crystal molecules in the region betweenthe pixel electrodes 6A, 6B, are increased. Consequently, the spray-bendalignment smoothly takes place.

[0213] To make the electric field generated between the protrusion 6 cand the corresponding recess 6 d stronger, a distance 6 e between theprotrusion 6 c and the recess 6 d may be set as small as possible.Nevertheless, it should be remembered that there is some limitation inreduction of the distance 6 e, because if the distance 6 e is reduced toexcess, shorting might occur between the pixel electrodes 6.Specifically, it is preferable that the distance 6 e is approximately4-8 μm.

[0214] Moreover, the flattening layer may be provided similarly to thesecond embodiment and the color filter layer may be provided on the sideof the array substrate similarly to the third embodiment.

[0215] (Tenth Embodiment)

[0216] A tenth embodiment of the present invention illustrates a liquidcrystal display capable of reliably performing spray-bend transition byproviding an intermediate portion between a main portion and an endportion of the pixel electrode, which differs from the constitution ofthe ninth embodiment.

[0217]FIG. 26 is a plan view schematically showing a consitution of mainelements of a liquid crystal display panel included in a liquid crystaldisplay of this embodiment. Hereinbelow, for the sake of convenience, apixel electrode 6A and a pixel electrode 6B adjacent to the pixelelectrode 6A in the length direction of the source line 11 arediscussed.

[0218] Referring to FIG. 26, the pixel electrode 6A overlaps with thestorage capacitor electrodes 9 at end portions where a plurality ofprotrusions 6 c in the length direction of the source line 11 areformed. End portion of the pixel electrode 6B which is opposed to theend portion where the protrusions 6 c are provided are protruded towardthe storage capacitor electrode 9 so as to overlap with the storagecapacitor electrode 9. Recesses 6 d corresponding to the plurality ofprotrusions 6 c are formed in the region of the protruded portion of thepixel electrode 6B which overlap with the storage capacitor electrode 9.

[0219] Similarly to the first embodiment, the pixel electrode 6 overlapswith the storage capacitor electrode 9 with the insulating layerinterposed therebetween.

[0220] The pixel electrode 6 is comprised of a main portion, endportions and intermediate portions 601 each of which is provided betweenthe main portion and each of the end portions. In the pixel electrode 6,the width 60 f of the intermediate portions 601 is set smaller than thewidth of the main portion and the width of the end portions and,specifically set to 10 μm or less.

[0221] Since the other elements are identical to those of the ninthembodiment, the same or corresponding parts are denoted by the samereference numerals and as such will not be described herein.

[0222] The storage capacitance formed between the protrusion 6 c and thecorresponding recess 6 d formed at end portion of the pixel electrode 6varies depending on the width and length of the intermediate portion601. So, by adjusting the width and length of the intermediate portion601 depending on the amount of the storage capacitance formed in eachpixel, the storage capacitance generated between the protrusion 6 c andthe recess 6 d and the storage capacitance generated by the otherelements can be well-balanced.

[0223] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, theelectric field concentration occurs between the protrusion 6 c and thecorresponding recess 6 d, similarly to the ninth embodiment. As aresult, the liquid crystal molecules around the region between theprotrusion 6 c and the recess 6 d become the transition nucleus and thespray-bend transition reliably takes place. Consequently, a high-qualityliquid crystal display capable of providing a satisfactory image withoutdot defect is obtained.

[0224] (Eleventh Embodiment)

[0225] An eleventh embodiment of the present invention illustrates aliquid crystal display capable of reliably performing spray-bendtransition by providing apertures in the counter electrode formed on theinner surface of the opposing substrate.

[0226]FIG. 27 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display of this embodiment. FIG. 28 is a cross-sectional viewtaken in the direction of arrows substantially along line XXVIII-XXVIIIof FIG. 27. FIG. 27 shows the positional relationship between the blackmatrix 22 and the counter electrode 2 and the other elements areomitted.

[0227] Referring to FIGS. 27, 28, the liquid crystal cell 101 comprisesthe color filter 102 and the array substrate 103 which are opposed toeach other with the spacer (not shown) interposed therebetween. Sincethe array substrate 103 is constituted similarly to that of the firstembodiment, the same or corresponding parts are denoted by the samereference numerals, and as such will not be described herein.

[0228] The color filter substrate 102 has the glass substrate 1. A colorfilter layer 21 is formed on the lower surface of the glass substrate 1.Specifically, the red color filter 21R, the green color filter 21G, andthe blue color filter 21B are formed and conductive black matrixes 23are formed at boundaries of these color filters.

[0229] The counter electrode 2 and the alignment layer 3 are formed onthe lower surface of the color filter layer 21. The counter electrode 2is divided for every pixel line to apply the voltage for every pixelline and the conductive black matrix 23 is placed so as to overlap withthe gap between the adjacent counter electrodes 2. Hereinafter, for thesake of convenience, a counter electrode 2A and a counter electrode 2Badjacent to the counter electrode 2A in the length direction of the gateline (not shown) are discussed.

[0230] Part of the counter electrode 2A is protruded toward the counterelectrode 2B for every pixel and the protruded portion has a shapesimilar to that of the end portion of the pixel electrode 6 of the tenthembodiment. More specifically, the protruded portion has a plurality ofprotrusions 2 c extended toward the length direction of the gate line.Part of the counter electrode 2B is protruded toward the counterelectrode 2A for every pixel as opposed to the protruded portion wherethe protrusions 2 c are provided. The protruded portion of the counterelectrode 2B has recesses 2 d corresponding to the protrusions 2 c.These protruded portions and the mains portions of the counterelectrodes 2A, 2B are connected by means of the intermediate portions201.

[0231] In this embodiment, the color filter layer 21 functions as theinsulator between the counter electrode 2 and the black matrix 23.

[0232] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, andsimultaneously, the transition voltage different from that applied tothe counter electrode 2 is applied to the black matrix 23, the electricfield concentration occurs between the protrusion 2 c and thecorresponding recess 2 d. Thereby, the liquid crystal molecules aroundthe region between the protrusion 2 c and the corresponding recess 2 dbecome transition nucleus and the spray-bend transition reliably takesplace. Consequently, a high-quality liquid crystal display capable ofproviding a satisfactory image without dot defect is obtained.

[0233] By thus generating the transition nucleuses on the side of theopposing substrate (color filter substrate), more transition nucleusesare generated as compared to the case where the transition nucleuses aregenerated only on the side of the array substrate. Consequently,reliability of the spray-bend transition is further improved.

[0234] (Twelfth Embodiment)

[0235] A twelfth embodiment of the present invention illustrates aliquid crystal display in which the shape of end portions of the pixelelectrode is different from that of the tenth embodiment.

[0236]FIG. 29 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display of this embodiment. As shown in FIG. 29, similarly tothe tenth embodiment, the pixel electrode 6 is comprised of a mainportion, end portions, and intermediate portions 601 each of which isprovided between the main portion and each of the end portions. Thewidth of the intermediate portion 601 is set smaller than the width ofthe main portion and the width of the end portions. Hereinbelow, for thesake of convenience, the pixel electrode 6A and the pixel electrode 6Badjacent to the pixel electrode 6A in the length direction of the sourceline 11 are discussed.

[0237] The pixel electrode 6A overlaps with the storage capacitorelectrode 9 at end portion where a plurality of protrusions 6 c extendedin the length direction of the source line 11 are formed. Theprotrusions 6 c are saw-tooth shaped and long sides 6 g and short sides6 h of the protrusions 6 c respectively make predetermined angles withrespect to the length direction of the gate line 12.

[0238] End portion of the pixel electrode 6B which is opposed to the endportion of the pixel electrode 6A where the protrusions 6 c are providedis protruded toward the storage capacitor electrode 9 so as to overlapwith the storage capacitor electrode 9. The recesses 6 d correspondingto the plurality of protrusions 6 c are formed in the region of theprotruded portion of the pixel electrode 6B which overlap with thestorage capacitor electrode 9.

[0239] Similarly to the first embodiment, the pixel electrode 6 overlapswith the storage capacitor electrode 9 with the insulating layerinterposed therebetween.

[0240] Since the other elements are identical to those of the ninthembodiment, the same or corresponding parts are denoted by the samereference numerals and as such will not be described herein.

[0241] When the direction in which the long side 6 g or the short side 6h of the protrusion 6 c extends coincides with the direction ofalignment treatment performed on the alignment layer, the strongestelectric field is generated in the liquid crystal layer. It is thereforedesirable that the direction in which the long side 6 g or the shortside 6 h extends conforms to the direction of the alignment treatment.Thereby, stronger electric field can be generated and consequently thespray-bend transition more reliably takes place.

[0242] In some cases, by varying the viewing angle characteristicdepending on the position in a display screen, satisfactory imagedisplay as a whole is achieved. In such cases, the viewing anglecharacteristic is often varied by changing the direction of thealignment treatment depending on the position in the display screen.Therefore, the direction in which the long side 6 g or the short side 6h of the protrusion 6 c extends may be varied for every pixel to beadapted to the change in the direction of alignment treatment.

[0243] (Thirteenth Embodiment)

[0244] A thirteenth embodiment illustrates a liquid crystal display inwhich the shape of end portions of the pixel electrode is different fromthat of the tenth embodiment.

[0245]FIG. 30 is a plan view schematically showing a constitution ofmain elements of a liquid crystal display panel included in a liquidcrystal display of this embodiment. As shown in FIG. 30, similarly tothe tenth embodiment, the pixel electrode 6 is comprised of a mainportion, end portions, and intermediate portions 601 each of which isprovided between the main portion and each of the end portions. Thewidth of the intermediate portion 601 is set smaller than the width ofthe main portion and the width of the end portions. Hereinbelow, for thesake of convenience, the pixel electrode 6A and the pixel electrode 6Badjacent to the pixel electrode 6A in the length direction of the sourceline 11 are discussed.

[0246] The pixel electrode 6A has portion protruded toward the storagecapacitor electrode 9 such that the protruded portion overlaps with thestorage capacitor electrode 9. A plurality of protrusions 60 a areformed in the region overlapping with the storage capacitor electrode 9so as to extend in the length direction of the storage capacitorelectrode 9.

[0247] End portion of the pixel electrode 6B which is opposed to the endportion of the pixel electrode 6A where the protrusions 60 aare providedis protruded toward the storage capacitor electrode 9 so as to overlapwith the storage capacitor electrode 9. Recesses 60 b corresponding tothe plurality of protrusions 60 a are formed in the region of theprotruded portion of the pixel electrode 6B which overlap with thestorage capacitor electrode 9.

[0248] Similarly to the first embodiment, the pixel electrode 6 overlapswith the storage capacitor electrode 9 with the insulating layerinterposed therebetween.

[0249] Since the other elements are identical to those of the ninthembodiment, the same or corresponding parts are denoted by the samereference numerals and as such will not be described herein.

[0250] When the transition voltage of the first embodiment is applied inthe liquid crystal display of this embodiment so constituted, theelectric field concentration occurs between the protrusion 60 a and thecorresponding recess 60 b, similarly to the ninth embodiment. As aresult, the liquid crystal molecules around a region between theprotrusion 60 a and the corresponding recess 60 b become the transitionnucleus and the spray-bend transition reliably takes place.Consequently, a high-quality liquid crystal display capable of providinga satisfactory image without dot defect is obtained.

[0251] (Fourteenth Embodiment)

[0252] A fourteenth embodiment of the present invention illustrates aliquid crystal display that employs a field sequential color method andis capable of reliably performing spray-bend transition.

[0253]FIG. 31 is a cross-sectional view schematically showing aconstitution of a liquid crystal display according to this embodiment.Referring to FIG. 31, the liquid crystal display of this embodimentcomprises a liquid crystal display panel 100, which is one of the liquidcrystal display panels described in the first through thirteenthembodiments, and a backlight 70 placed below the liquid crystal displaypanel 100.

[0254] The backlight 70 comprises a light guiding plate 72 comprised oftransparent rectangular synthetic resin plate, a light source 71 placedin the vicinity of an end face 72 a of the light guiding plate 72 asopposed to the end face 72 a, a reflector 73 placed below the lightguiding plate 72, and a light diffusing sheet 74 provided on an uppersurface of the light guiding plate 72.

[0255] The light source 71 is a LED array in which LEDs (light emittingdiodes) for emitting light of three primary colors—red, green, and blue,are sequentially and repeatedly arranged.

[0256] In the backlight 70 so constituted, the light emitted from thelight source 71 is incident on the light guiding plate 72 through theend face 72 a. The incident light is multiple-scattered inside of thelight guiding plate 72 and emanates from the entire upper surfacethereof. In this case, the light leaking downward from the light guidingplate 72 and incident on the reflector 73 is reflected by the reflector73 and returned to the inside of the light guiding plate 72. The lightemanating from the light guiding plate 72 is diffused by the lightdiffusing sheet 74 and the resulting diffused light is incident on theliquid crystal display panel 100. Thereby, the liquid crystal displaypanel 100 is entirely and uniformly irradiated with red, green, or bluelight.

[0257] In the liquid crystal display panel of this embodiment soconstituted, a control circuit (not shown) outputs a control signal tothe backlight 70 to cause the LEDs as the light source of the backlight70 to sequentially emit light of red, green, and blue in a predeterminedcycle. To perform display in synchronization with the emission of light,the control circuit outputs a control signal to a gate driver (notshown) and a source driver (not shown), in accordance with the imagesignal externally input. As a result, the gate driver applies a scanningsignal voltage to the gate lines, thereby causing the TFTs of therespective pixels to be sequentially turned on, and according to thistiming, the source driver sequentially applies an image signal voltageto the pixel electrodes of the respective pixels through the sourcelines. Thereby, the liquid crystal molecules are modulated and lighttransmittance of light emitted from the backlight 70 changes. As aresult, an image according to the image signal is presented to a viewerwho is observing the liquid crystal display.

[0258] As described above, the liquid crystal display of this embodimentemploys so-called field sequential color method. In case of the liquidcrystal display by the field sequential color method, since one frameperiod is divided into a plurality of sub-frame periods in display, asatisfactory image display is not obtained if the response of the liquidcrystal display panel is slow. On the other hand, since the liquidcrystal display of this embodiment comprises the OCB-mode liquid crystaldisplay panel 100 capable of high-speed response, a satisfactory imagedisplay can be achieved by the field sequential color method.

[0259] As thus far described, the liquid crystal display panelsillustrated in the first to thirteenth embodiments are capable ofreliably performing spray-bend transition. Therefore, in the liquidcrystal displays of these embodiments, a satisfactory image displaywithout a dot defect is obtained.

[0260] (Fifteenth Embodiment)

[0261] A fifteenth embodiment of the present invention illustrates aliquid crystal display capable of reliably performing spray bendtransition by providing the source electrode so as to overlap with thegate line. Since the constitution of the liquid crystal display of thisembodiment is identical to that of the first embodiment except thestructure of the pixel described with reference to FIG. 32, descriptionthereof is omitted.

[0262]FIG. 32 is a plan view schematically showing a constitution of astructure of a pixel in the liquid crystal display of this embodiment.As shown in FIG. 32, the pixel is connected to the source line 11provided with a source electrode 111 to which a signal voltage is to besupplied through the source line 11. The source electrode 111 extends inthe length direction of the gate line 12 and overlaps with the gate line12 with an insulator (not shown) interposed therebetween. The signalvoltage is supplied to the source electrode 111 and then to the pixelelectrode through a drain electrode. A liquid crystal layer (not shown)is disposed above the source line 11. That is, the source electrode 111is interposed between the gate line 12 and the liquid crystal layer.

[0263] The source electrode 111 has a bent portion in a region thereofoverlapping with the gate line 12. When a transition voltage describedlater is applied in the liquid crystal display of this embodiment soconstituted, the electric field concentration occurs between the bentportion of the source electrode 111 and the pixel electrode 6. As aresult, liquid crystal molecules around a region between the bentportion and the pixel electrode 6 become transition nucleus and thespray-bend transition reliably takes place.

[0264] Subsequently, waveforms of the transition voltage in the liquidcrystal display of this embodiment and a method for applying thetransition voltage will be explained.

[0265]FIG. 33 is a view showing waveforms of the transition voltage inthe liquid crystal display of this embodiment. In the liquid crystaldisplay of this embodiment, as show in FIG. 33, +15V voltage as agate-on potential is applied to respective gate lines 12 a, 12 b, 12 c .. . for one second. Likewise, +25V voltage is applied to the counterelectrode 2 for one second. During this application, an AC rectangularwave voltage is applied to the source lines 11 at +7V and 30 Hz (fieldfrequency), and in a duty ratio of 0.5 1. More specifically, similarlyto the first embodiment, the voltage is applied to the source lines 11in such a manner that the AC rectangular wave voltage applied to thepixel electrode 6Aa, 6Cc, . . . , through source lines 11A, 11C . . . onodd columns and the AC rectangular wave voltage applied to the pixelelectrodes 6Bb, 6Dd . . . through the source lines 11B, 11D . . . oneven columns are reversed in polarity.

[0266] As the result of the application of the transition voltage, thespray-bend transition can uniformly take place in a comparativelylarge-sized liquid crystal display. This is due to the fact that the ACvoltage applied to the liquid crystal causes unstable disturbance,thereby resulting in improved uniformity. The field frequency of thetransition voltage is not limited 30 Hz. According to study by inventorsor the like, it is desirable that the frequency is 1 kHz or less.

[0267] As an alternative, transition voltage of waveforms shown in FIG.34 may be employed. In that case, differently from the case of FIG. 33,no voltage is applied to the pixel electrode 6 by keeping the sourceline 11 at potential of 0V and −25V voltage is applied to the counterelectrode 2 for one second. Since the potential of the source line 11 iskept at 0V and is not fluctuated, application of the transition voltageis easily carried out without depending on the source driver. Also inthat case, the spray bend transition reliably takes place similarly tothe case using the transition voltage of the waveforms of FIG. 33. Inactuality, however, slight nonuniformity of spray-bend transition isobserved in the plane and the voltage required for generating thespray-bend transition is approximately 2 to 3 V higher as compared tothe case of FIG. 33.

[0268] By the way, the inventors or the like found that the spray-bendtransition is facilitated when the potential applied to the counterelectrode 2 and the gate-on potential have the same polarity as comparedto the case using voltages of different polarities (e.g., −25V voltageis applied to the counter electrode 2 and +15V is applied to the gateline 12 as the gate-on potential). This might be due to the fact thatthe transversal electric field generated using the voltages of the samepolarity is stronger than that generated using the voltages of differentpolarities and the spray-bend transition is thereby facilitated.

[0269] As a further alternative, the transition voltage of the waveformsshown in FIG. 35 may be employed. Similarly to the case of FIG. 9, +15Vvoltage as the gate-on potential is sequentially applied to therespective gate lines 12 a, 12 b, 12 c . . . , while −25V voltage isapplied to the counter electrode 2 for one second. During thisapplication, an AC rectangular wave voltage is applied to the sourcelines 11 at ±7V and 30 Hz (field frequency) and in the duty ratio of0.5:1. In that case, since the gate lines 12 are driven in the samemanner that an image is normally displayed, the gate driver provided inthe general liquid crystal display (e.g., TN-type liquid crystaldisplay) can be used. Therefore, inexpensive constitution is realized.

[0270] Similarly to the first embodiment, it is desirable that novoltage is applied across the pixel electrode 6 and the counterelectrode 2 just before the transition voltage is applied, in thisembodiment.

[0271] The liquid crystal displays comprising the OCB-mode liquidcrystal display panels have been thus far described. The presentinvention is not limited to these and may be employed in liquid crystaldisplays comprising liquid crystal display panels which have a displayalignment state and a non-display alignment state which differ from eachother and require the initialization for changing the non-displayalignment state to the display alignment state before an image isdisplayed.

[0272] As should be appreciated from the forgoing description, theliquid crystal displays of the present invention are capable ofobtaining a preferable image display without dot defect. These liquidcrystal displays are applicable to various products, including liquidcrystal televisions, liquid crystal monitors, liquid crystal displays ofportable phones, etc.

[0273] Numerous modifications and alternative embodiments of theinvention will be apparent to those skilled in the art in view of theforegoing description. Accordingly, the description is to be construedas illustrative only, and is provided for the purpose of teaching thoseskilled in the art the best mode of carrying out the invention. Thedetails of the structure and/or function may be varied substantiallywithout departing from the spirit of the invention.

What is claimed is:
 1. A liquid crystal display comprising: a pair ofopposed substrates; a liquid crystal layer disposed between the pair ofsubstrates, the liquid crystal layer having a display alignment stateand a non-display alignment state which differ from each other and beingsubjected to an initialization process so as to be changed from thenon-display alignment state to the display alignment state before animage is displayed; a first electrode provided on one of the pair ofsubstrates; a second electrode provided so as to overlap with the firstelectrode with an insulator interposed therebetween and disposed betweenthe first electrode and the liquid crystal layer, the second electrodehaving a lack portion in a region overlapping with the first electrode;and drive means for generating potential difference between the firstelectrode and the second electrode to thereby perform the initializationprocess.
 2. The liquid crystal display according to claim 1, wherein oneof the pair of substrates is an array substrate having a plurality ofpixel electrodes provided in matrix; a plurality of gate lines andsource lines arranged so as to cross each other; a plurality ofswitching devices provided as corresponding to the respective pixelelectrodes, for switching between a conductive state and anon-conductive state between the pixel electrodes and the source linesin accordance with a drive signal supplied through the source lines, andthe other of the pair of substrates is an opposing substrate having acounter electrode opposed to the array substrate.
 3. The liquid crystaldisplay according to claim 2, further comprising storage capacitorelectrodes overlapping with the pixel electrodes, wherein the firstelectrode is the storage capacitor electrode and the second electrode isthe pixel electrode.
 4. The liquid crystal display according to claim 2,wherein the first electrode is the gate line and the second electrode isthe pixel electrode.
 5. The liquid crystal display according to claim 2,further comprising storage capacitor electrodes overlapping with thepixel electrodes, wherein the first electrode is the storage capacitorelectrode and the second electrode is the source line.
 6. The liquidcrystal display according to claim 2, wherein the first electrode is thegate line and the second electrode is the source line.
 7. The liquidcrystal display according to claim 2, wherein the first electrode is thepixel electrode and the second electrode is the gate line.
 8. The liquidcrystal display according to claim 2, further comprising storagecapacitor electrodes overlapping with the pixel electrodes, wherein thefirst electrode is the pixel electrode and the second electrode is thestorage capacitor electrode.
 9. The liquid crystal display according toclaim 2, wherein the first electrode is the source line and the secondelectrode is the gate line.
 10. The liquid crystal display according toclaim 2, further comprising storage capacitor electrodes overlappingwith the pixel electrodes, wherein the first electrode is the sourceline and the second electrode is the storage capacitor electrode. 11.The liquid crystal display according to claim 1, wherein the potentialdifference is 15V-32V.
 12. The liquid crystal display according to claim1, further comprising: a third electrode and a fourth electrode providedon one of the pair of substrates on which the first and secondelectrodes are not provided, so as to overlap each other with aninsulator interposed therebetween, wherein the third electrode isdisposed between the fourth electrode and the liquid crystal layer andhas a lack portion in a region overlapping with the fourth electrode,and wherein the drive means is adapted to generate potential differencebetween the third electrode and the fourth electrode to perform theinitialization process.
 13. The liquid crystal display according toclaim 1, wherein the lack portion is an aperture provided in the secondelectrode.
 14. The liquid crystal display according to claim 13, whereinthe aperture includes a plurality of straight-line portions extendingtoward a position at which these portions cross each other.
 15. Theliquid crystal display according to claim 13, wherein the aperture isV-shaped.
 16. The liquid crystal display according to claim 13, whereinthe aperture is W-shaped.
 17. The liquid crystal display according toclaim 13, wherein the aperture is X-shaped.
 18. The liquid crystaldisplay according to claim 13, wherein the aperture is polygon-shaped.19. The liquid crystal display according to claim 1, wherein the lackportion is shaped to enable application of two-direction electric fieldsto the liquid crystal layer.
 20. The liquid crystal display according toclaim 13, wherein the second electrode has an aperture including aportion which is 4 μm wide or less.
 21. The liquid crystal displayaccording to claim 1, wherein the lack portion is a cutout portionprovided in the second electrode.
 22. The liquid crystal displayaccording to claim 1, wherein the non-display alignment state is sprayalignment and the display alignment state is bend alignment.
 23. Aliquid crystal display comprising: a pair of opposed substrates; aliquid crystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed; a first electrode and a second electrode formed on one of thepair of substrates so as to overlap each other with an insulatorinterposed therebetween; drive means for generating potential differencebetween the first electrode and the second electrode to perform theinitialization process; and convex portions respectively formed atopposed positions in the pair of the substrates such that the convexportions are protruded in the thickness direction of the liquid crystallayer.
 24. A liquid crystal display having: a pair of opposedsubstrates; and a liquid crystal layer disposed between the pair ofsubstrates, the liquid crystal layer having a display alignment stateand a non-display alignment state which differ from each other and beingsubjected to an initialization process so as to be changed from thenon-display alignment state to the display alignment state before animage is displayed; comprising: a first electrode provided on one of thepair of substrates; a second electrode disposed between the firstelectrode and the liquid crystal layer; and drive means for generatingpotential difference between the first electrode and the secondelectrode to thereby perform the initialization process, wherein opposedend portions of two adjacent second electrodes overlap with the firstelectrode with an insulator interposed therebetween.
 25. The liquidcrystal display according to claim 24, wherein one of the opposed endportions has a protrusion in a region overlapping with the firstelectrode and the other end portion has a recess corresponding to theprotrusion in a region overlapping with the first electrode.
 26. Theliquid crystal display according to claim 25, wherein distance betweenthe protrusion and the recess is 4 μm-8 μm.
 27. The liquid crystaldisplay according to claim 25, wherein the protrusion is saw-toothshaped.
 28. The liquid crystal display according to claim 24, whereinone of the pair of substrates is an array substrate having a pluralityof pixel electrodes provided in matrix; a plurality of gate lines andsource lines arranged so as to cross each other; a plurality ofswitching devices provided as corresponding to the respective pixelelectrodes, for switching between a conductive state and anon-conductive state between the pixel electrodes and the source linesin accordance with a drive signal supplied through the gate lines, andthe other of the pair of substrates is an opposing substrate having acounter electrode opposed to the array substrate.
 29. The liquid crystaldisplay according to claim 28, further comprising storage capacitorelectrodes overlapping with the pixel electrodes, wherein the firstelectrode is the storage capacitor electrode and the second electrode isthe pixel electrode.
 30. The liquid crystal display according to claim28, wherein the first electrode is the gate line and the secondelectrode is the pixel electrode.
 31. The liquid crystal displayaccording to claim 24, wherein the insulator is a color filter.
 32. Theliquid crystal display according to claim 24, wherein the insulator is aflattening layer.
 33. The liquid crystal display according to claim 28,wherein an intermediate portion is formed between a main portion of thesecond electrode and the end portion of the second electrode so as tohave a width smaller than a width of the main portion and a width of theend portion.
 34. The liquid crystal display according to claim 28,wherein the first electrode is comprised of a conductive mask and thesecond electrode is the counter electrode.
 35. The liquid crystaldisplay according to claim 24, wherein the potential difference is15V-32V.
 36. The liquid crystal display according to claim 24, whereinvoltages of different polarities are respectively applied to adjacentpixel electrodes.
 37. The liquid crystal display according to claim 24,wherein the non-display alignment state is spray alignment and thedisplay alignment state is bend alignment.
 38. The liquid crystaldisplay according to claim 1, further comprising: an illuminating devicehaving a light source for emitting red light, green light, and bluelight; and illuminating device control means for controlling theilluminating device so as to emit the red light, the green light and theblue light by time division within one frame period.
 39. A liquidcrystal display comprising: a pair of opposed substrates; a liquidcrystal layer disposed between the pair of substrates, the liquidcrystal layer having a display alignment state and a non-displayalignment state which differ from each other and being subjected to aninitialization process so as to be changed from the non-displayalignment state to the display alignment state before an image isdisplayed, wherein one of the pair of substrates is an array substratehaving a plurality of pixel electrodes provided in matrix; a pluralityof gate lines and source lines arranged so as to cross each other; aplurality of switching devices provided as corresponding to therespective pixel electrodes, for switching between a conductive stateand a non-conductive state between the pixel electrodes and the sourcelines in accordance with a drive signal supplied through the gate lines,and the other of the pair of substrates is an opposing substrate havinga counter electrode opposed to the array substrate, and wherein a sourceelectrode constituting the switching device extends from the source linein parallel with the gate line so as to overlap with the gate line andis interposed between the gate line and the liquid crystal layer, andwherein a drive signal for causing conduction between the pixelelectrode and the source line is supplied to the gate line to set thesource electrode and the pixel electrode at equipotential, and potentialdifference is generated between the source line and the gate line tothereby perform the initialization process.
 40. The liquid crystaldisplay according to claim 39, wherein potential difference is generatedbetween the counter electrode and the pixel electrode to thereby performthe initialization process.
 41. The liquid crystal display according toclaim 39, wherein the source electrode has a bent portion.